The invention relates to a fuser, and in particular to a fuser for a laser printer.
Generally, a conventional laser printer bonds toner (carbon powder) to print media sheets using heating and pressure. A heat source of the conventional laser printer may comprise a halogen lamp or a ceramic heater.
Referring to FIG. 1, after a media sheet P enters a conventional laser printer 1, a laser scan unit (LSU) 11 projects laser light carrying image data to a sensitization roller 12. Carbon powder in a toner cartridge 13 is fixed to an imaging area on the sensitization roller 12 by operation of a roller 14. The rotating sensitization roller 12 continuously applies the carbon powder having the image data to the media sheet P. The media sheet P then passes through a fuser 15 and the carbon powder thereon is securely bonded to the media sheet P thereby.
Referring to FIG. 2, the fuser 15 comprises a hollow heating roller 16, a pressurization roller 17, and a halogen lamp 18. The halogen lamp 18 is disposed in the hollow heating roller 16, and the pressurization roller 17 rotatably contacts the hollow heating roller 16. When the carbon powder is bonded to the paper sheet P by the fuser 15, the halogen lamp 18 generates and outputs heat to a peripheral surface of the hollow heating roller 16 by thermal radiation. By rotation of the hollow heating roller 16 and pressurization roller 17, heating of the hollow heating roller 16, and pressurization of the pressurization roller 17, the carbon powder is continuously and securely bonded to the media sheet P.
The fuser 15, however, has many drawbacks. Transmitted to the peripheral surface of the hollow heating roller 16 by thermal radiation, heat generated by the halogen lamp 18 must be significantly increased. Moreover, as the halogen lamp 18 is disposed in the hollow heating roller 16, the hollow heating roller 16 is required to have a predetermined size. Namely, the hollow heating roller 16 has a large peripheral surface area. At this point, time required to transmit the heat from the halogen lamp 18 to the peripheral surface of the hollow heating roller 16 is increased. Accordingly, preheating time required by the fuser 15 is increased, causing increased electrical consumption of the laser printer 1 and inconvenience. Additionally, as the fuser 15 is not provided with any effective thermal insulation, much heat is dissipated into the laser printer 1 from the peripheral surface of the hollow heating roller 16, reducing the efficiency of thermal utilization of the halogen lamp 18 and increasing the temperature of other elements. Thus, the laser printer 1 is easily damaged.
Additionally, conventional fusers may use a ceramic heater rather than a halogen lamp. The ceramic heater, however, is very expensive. Moreover, the inner structure of the fuser disposed with the ceramic heater is complicated.